1. Field of the Invention
The present invention relates to a casting process comprising placing a breakable core into a cavity in a mold and pouring a molten metal under a pressure into the cavity by means of a plunger.
2. Description of the Prior Art
In such conventional casting processes, the speed of movement of the plunger has been controlled to linearly increase with a given ratio of time to distance, and the pressure applied to a molten metal has been controlled to suddenly increase.
However, there are problems which arise in such conventional casting processes. If the speed of the plunger is linearly increased as described above, the molten metal may undergo a wave and include a gas such as air thereinto, so that casting defects such as casting cavities may be produced in the resulting cast product. In addition, if the pressure applied to the molten metal by the plunger is controlled to suddenly increase, the core may be broken under the influence of that pressure.